Support for Hermes on iOS (RN 0.64)

[mrousavy]

The first release candidate of 0.64 relased (React Native 0.64-rc0), which includes support for using the Hermes JS Executor on iOS.

While it's still a pre-release, it makes sense to support it once 0.64 officially releases, as now CodePush does not work with hermes enabled on iOS.

Is this already planned?

[mrousavy]

Of course the appcenter codepush command needs to be able to create the Hermes bundle on iOS first, so I've created an issue for that here: microsoft/appcenter-cli#1164

[gilbertl]

Our app is on rc64-2 with Hermes enabled on iOS. I just made a codepush OTA update to our app and it worked perfectly.

What am I missing?

[mrousavy]

@gilbertl how did you create the bundle?

[gilbertl]

We run

appcenter codepush release-react -d #{ENV['IOS_CODEPUSH_DEPLOYMENT_NAME']} -a #{ENV['APPCENTER_USERNAME']}/#{ENV['IOS_APPCENTER_APP_ID']} --target-binary-version \"#{targetVersion}\" --description \"#{release_notes}\" --disable-duplicate-release-error

to bundle and release the update

[a-eid]

@mrousavy could you please let us know if this works for you ( with hermes enabled on IOS ) ?

[mrousavy]

Works for me now. Not sure what the original issue was, maybe I had a weird node version.

[ivanmoskalev]

@mrousavy @gilbertl The bundle that gets built is an old text-based jsbundle and not Hermes bytecode.

[mrousavy]

@ivanmoskalev can you elaborate? How did you find that out? Does it still run when it's text-based?

[ivanmoskalev]

@mrousavy It does run, Hermes supports running JS source.

How I found this out: in the Appcenter portal there is a button that allows you to download the Codepush update bundle that gets served by the Appcenter to your users. You can access by clicking on a specific CP deployment.

I pressed it and inspected the iOS Codepush bundle manually. It contained JS source.

When I checked the Android Codepush bundle the same way, it had Hermes bytecode.

Then I checked appcenter-cli sources and found out that the algorithm that determines whether the release-react should run hermesc when building is implemented only for Android.

[mrousavy]

I see, that is a problem. I assume this affects overall app performance, as the bundle is not fully optimized in that case. I'll reopen this issue then, hopefully a maintainer might look at this. Could you create an issue at the appcenter-cli repo in the meantime? @ivanmoskalev

cc @alexandergoncharov or other maintainers

[ivanmoskalev]

I went ahead and created microsoft/appcenter-cli#1399

[alexandergoncharov-zz]

Hi there,

Thanks for reopening the issue.

Hermes for IOS is on our roadmap but we don't have ETA for this.
We will do it as soon as possible and will keep this issue and others posted.

Thanks,
Alexander

[BANG88]

@alexandergoncharov Any updates ?. 😄

Thanks.

[ivanmoskalev]

@BANG88 this has been fixed (see microsoft/appcenter-cli#1399)!

[BANG88]

@ivanmoskalev https://github.com/microsoft/appcenter-cli/blob/2680289793d861a294c9e8d1a680abe3a6b7e72a/src/commands/codepush/lib/react-native-utils.ts#L403

I have checked here looks like only Android ATM.

[ivanmoskalev]

@BANG88 Check microsoft/appcenter-cli@3128d37 – you might want to use a version that includes this commit.

[BANG88]

@ivanmoskalev Sorry dude. I don't know which version include iOS Hermes Support. 😭

[alexandergoncharov-zz]

Hi all,

Yeah, the latest version of the appcenter-cli has support for iOS Hermes. Sorry that I didn't mention it in this issue.
@ivanmoskalev , could you please test it on the latest appcenter-cli version?

@BANG88 , thanks for help :)

[bryansum]

Probably fine to close this issue right? It being open made me think it wasn't supported yet (it is!). Excited to try this out